[sdiy] first filter ?

[dustin sedlacek]

thanks for the tip 

On 6/16/05, harrybissell <harrybissell at prodigy.net> wrote:
> 
> LOL... laymen terminology ? no...
> 
> (Sallen and Key were two men who published a filter circuit that could
> be a highpass or a lowpass filter... or a bandpass filter by rearranging
> 
> the resistors and capacitors)
> 
> Their circuit uses a single gain stage (transistors or opamp) and gives
> a
> 12dB cutoff slope (6dB for the bandpass).
> 
> EDN magazine has an article in their June 5th (or so, the latest one) on
> filters
> that has the schematic for the Sallen Key.
> 
> Texas Instruments has an application note on the Sallen Key filter as
> well iirc.
> www.ti.com <http://www.ti.com>
> 
> As I said... the lopass gate IS a Sallen-Key filter. Best way to study
> it is to draw
> a copy of the schematic with the switch removed (ie drawn with only the
> LPF components and drawn with only the VCA components) It will be easier
> to 'see'
> how similar they are.
> 
> over...
> 
> H^) harry
> 
> dustin sedlacek wrote:
> 
> > what is sallen key ? i have seen this term several times and googled
> > it even and i just dont understand , can i get some laymen terminolgy
> > ? and this looks like it is leading into can i make my own borg filter
> > ? or something simlar ?
> > On 6/15/05, harrybissell <harrybissell at prodigy.net> wrote:
> >
> > The low pass gate (in lowpass mode) is a Sallen Key filter.
> > It (by
> > itself)
> > has a 12dB slope. By playing with the gain of the opamp
> > after the two
> > optos, you should be able to get reaonance and even
> > oscillation.
> >
> > Be aware that Sallen Key filters are really ill behaved once
> > they
> > oscillate...
> > they will rip your head right off...
> >
> > H^) harry
> >
> >
> >
> > dustin sedlacek wrote:
> >
> > > i am looking to build a filter ...my first i like the low
> > pass gates ,
> > > they seem very cool and i understand that with 2 of them
> > and a basic
> > > mixer i can get resonance ? how is this ? what kind of
> > slope would i
> > > get ? 12/db ? can i get a sharper slope ? what about a 6
> > db slope ?
> > >
> > >
> > >
> > >
> > > sorry for the double post for some
> > >
> > > On 6/9/05, Ray Wilson < raywilson at comcast.net> wrote:
> > >
> > > Check
> > > out:
> > http://www.musicfromouterspace.com/analogsynth.php?page=ANALOG
> > Click
> > > filters. Cheers Ray
> > >
> > > ----- Original Message -----
> > > From: dustin sedlacek
> > > Cc: synth-diy at dropmix.xs4all.nl
> > > Sent: Thursday, June 09, 2005 1:15 AM
> > > Subject: [sdiy] first filter ?
> > >
> > >
> > > i am looking to build a filter ...my first i
> > like
> > > the low pass gates , they seem very cool and i
> > > understand that with 2 of them and a basic mixer
> > i
> > > can get resonance ? how is this ? what kind of
> > > slope would i get ? 12/db ? can i get a sharper
> > > slope ? what about a 6 db slope ?
> > >
> > >
> > >
> > >
> > > --
> > > Dustin
> >
> >
> >
> >
> >
> > --
> > Dustin
> 
> 


-- 
Dustin
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20050617/8e5a6f85/attachment.htm>